Feeling no pain.

You're about to get a vaccine, and a kindly nurse tells you, "Relax. I'm going to stick 400 needles in your arm, and you won't feel a thing." WHHAATTT??? That's right--painless needles!

Engineers Mark Prausnitz and Mark Allen at the Georgia Institute of Technology have developed a skin patch of microneedles (needles thinner and shorter than the diameter of a human hair), which they hope will eventually deliver painless medication.

In preliminary tests, and Allen stuck their needle patch into an armful of volunteers. "They felt a piece of tape and a mild sort of scratching if you wiggled the patch," reports Prausnitz. "But no pain."

Each needle in the 3mm square patch is less than 0.02 cm (0.006 in) long, and penetrates only the outermost layer of skin, the stratum corneum. The stratum corneum contains no nerve endings--thus, there's no sensation of pain. Any drug in the patch travels through the next layers of skin, the epidermis and dermis, which contain blood vessels that absorb and disperse medication to the bloodstream.

But unlike conventional needles that deliver medication to the blood in a matter of seconds, you might have to wear a microneedle patch longer. "In a situation where somebody needs a drugs quickly, you wouldn't use microneedles," says Prausnitz. But for routine vaccines, or for patients like diabetics who self-inject medication regularly, microneedles would offer shots without the pain.

Prausnitz envisions medication contained in the patch as a gel, covered with a plastic liner. (The microneedles are made of silicon, the same element used to make computer chips.) "It might look like a Band-aid," explains Prausnitz. "You could just peel off the plastic liner and stick it on." Enough needling!